IO2 FAMILIES AND GENERA. 



Onehidiidse, (PULMONATA.) Plate xx. 

 Onchidium, 318. 



Ostreidae. (PSEUDOLAMELLIBRANCHIATA.) Plate iii. 

 Ostrea, 32. 



Otinidse. (PULMONATA.) Plate xvii. 

 Otina, 204. 



Pandoridse. (EULAMELLIBRANCHIATA.) Plate xv. 

 Pandora, 172. 



Patellidse. (PROSOBRANCHIATA.) Plate xxi. 



Patella, shell conical ; crown near centre, 324. 

 Helcion, shell cap-shaped ; crown near margin, 325. 



PeCtinidSB. (PSEUDOLAMELLIBRANCHIA*TCA.) Plates iii., iv. 

 Pecten, 33 -43- 



Petrieolidse. (EULAMELLIBRANCHIATA.) Plate x. 



Petricola, 128. 



Philinidse. (OPISTHOBRANCHIATA.) Plate xxx. 

 Philine, 569-576. 



Pholadidse. (EULAMELLIBRANCHIATA.) Plate xiv. 



Pholas, apophyses long and partly hidden within the junction ; 

 shell prickly all over, 160-163. 



Pholadidea, apophyses long and partly hidden within the junction ; 

 anterior part covered with prickly ridges ; posterior end with 

 horny cup attached, 164. 



Xylophaga, apophyses short and prominent, 165. 



Physidse. (PULMONATA.) Plate xvii. 

 Physa, 227-229. 



Pletirobranehidse. (OPISTHOBRANCHIATA.) Plate xxx. 

 Pleurobranchus, 580, 581, 



PleUFOphyllidiidse. (OPISTHOBRANCHIATA.) Plate xxxii. 

 Pkurophyllidia, 601. 



PleUPOtomariidSB. (PROSOBRANCHIATA.) Plate xxi. 

 Scissurella, 334. 



